Re: '93 Suzuki Bandit Starting Problems (should I buy????)

Yonnermark wrote:

> HOWEVER, the only problem it has is that it can sometimes be hard to
> start. The owner says it should be "something and nothing" and I'm sure
> he is probably right but I thought I'd come here for a 2nd opinion. Is
> it possible/likely that this problem starting the bike could turn into
> something expensive? Once it is started it is reported to perform
> extremely well.

Well, it's probably operator ignorance causing the starting problem.
There's an epidemic of ignorance when it comes to motorcycle

The basic problem with Japanese motorcycles built after the 1980's is
that riders don't understand how the "choke" works. The constant vacuum
carburetors mandated by the EPA don't actually have a *real* choke,
i.e., there is NO choke plate like a car's carburetor would have.

Instead, CV carbs have a bypass starting enrichener which has a small
diameter passage that goes around the throttle butterfly. There is a
little plunger valve in the passage and that is what actually opens and
closes when you put the choke lever or knob in the ON position.

So air is sucked by engine vacuum through the bypass around the
throttle butterfly and gasoline is sucked right out of the float bowl
and the small amount of fuel/air mixture going through the bypass is
enough to start the engine and the engine should start IF
you don't touch the throttle twist grip at all.

Four stroke engines don't develop much vacuum in the intake tract,
because the intake strokes are rather far apart in time.

When you open the throttle while trying to start a motorcycle equipped
with a bypass starting enrichener, engine vacuum is reduced and the
engine cannot suck enough gasoline up to get started. The operator will
keep trying to start it until he runs his battery down and then he'll
be asking about why is his battery always dead and we have to go
through all that same old routine.

Just don't turn the throttle handle when starting the motorbike! It's
that simple.

The engine should start and run and be warming up while you are
standing beside the motorbike putting on your helmet and gloves. You
shouldn't have to be nursing the throttle or have to keep reducing the
setting of the "choke" lever, if your carbs are adjusted correctly and
they are clean.

One thing I always recommend to somebody who is having a hard time
starting his engine is to find the master idle knob and turn it
clockwise a turn or two to increase the
vacuum downstream of the throttle butterflies.

The other major problem is that constant vacuum carburetors have tiny
little idle passages. Although the idle jets themselves are HUGE
compared to a slide valve carburetor's idle jets, the single idle
mixture passage which is regulated by a tapered screw concealed under
an anti-tamper plug is CRITICAL to the smooth running of the engine.

And the epidemic of ignorance is at work here, too. The owners of
Japanese motorbikes don't know that they need to use chemical
carburetor cleaners regularly to keep their carburetors clean enough to
operate correctly. Instead, when the idle passages begin to plug up and
the engine stalls, they make the mistake of adjusting the master idle
knob to increase the idle RPM.

When they do that, the engine becomes hard to start. The decreased
vacuum in the intake tract is due to the throttle butterflies being
open too far!

Since the EPA doesn't want you to tamper with that idle mixture screw,
they've hidden it under the anti-tamper plug. The easiest way to clean
out the idle mixture passages is to add 3 or 4 ounces of Berryman's
B-12 Choke and Carburetor Cleaner to a full tank of gas and just go for
a ride. It's available in the US, I don't know what you might have
available where you're at.

Do not use fuel system cleaners containing petroleum distillate, those
are for cleaning and *lubricating* fuel injectors. Instead, you want a
carburetor cleaner containing xylene, acetone, and methyl alcohl to
dissolve the gum and varnish in the carburetor.

After several miles, the idle RPM will increase and you can stop and
turn the master idle knob down. It should be between the pair of
carburetors that are on the righthand side of the engine, unless there
is a flexible cable to adjust the idle RPM. In that case the adjuster
knob will be on the left side of the motorbike.


Relevant Pages

  • Re: 93 Suzuki Bandit Starting Problems (should I buy????)
    ... >carburetors mandated by the EPA don't actually have a *real* choke, ... >So air is sucked by engine vacuum through the bypass around the ... >vacuum downstream of the throttle butterflies. ... >little idle passages. ...
  • Re: Honda XL 600R
    ... It has a kick starting system ... > and the engine sounds great and has lots of power to the wheel when driving. ... Those old primitive carburetors didn't have a choke. ... you need to find out how to adjust the idle speed of BOTH of the ...
  • Re: Honda 650 starting problems when very hot
    ... Before you ride, find out where the idle speed knob is at, probably ... That's a symptom of dirty carburetors. ... start the engine when it's hot/ ... Could too much oil ...
  • Re: 99 katana 750 stalling
    ... start but the engine sounded kind of rough... ... The tiny idle mixture ... Raw gasoline is sucked straight out of the float bowls and into the ... You don't need to start tearing the carburetors off the engine to clean ...
  • Re: FAQ, Part 4/6
    ... If your antifreeze was just changed and your car started to overheat, ... Idle speed jumps OR Intermittent idle speed problems ... 2.5L engine knocks/ticks; poor cold idle ... Later I found a 6-way connector was loose. ...